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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 3 |
| 3 | 20 |
| 4 | 30 |
| 5 | 336 |
| 6 | 5040 |
| 7 | 7920 |
| 8 | 154440 |
| 9 | 3603600 |
| 10 | 5765760 |
| 11 | 160392960 |
| 12 | 5079110400 |
| 13 | 8204716800 |
| 14 | 296541907200 |
| 15 | 11861676288000 |
| 16 | 520431047136000 |
| 17 | 857180548224000 |
| 18 | 41430393164160000 |
| 19 | 2163102632570880000 |
| 20 | 3569119343741952000 |
[1,3,20,30,336,5040,7920,154440,3603600,5765760, 160392960,5079110400,8204716800,296541907200, 11861676288000,520431047136000,857180548224000, 41430393164160000,2163102632570880000, 3569119343741952000] |